bpftool: Add bpf_token show

Add `bpftool token show` command to get token info
from bpffs in /proc/mounts.

Example plain output for `token show`:
token_info  /sys/fs/bpf/token
	allowed_cmds:
	  map_create          prog_load
	allowed_maps:
	allowed_progs:
	  kprobe
	allowed_attachs:
	  xdp
token_info  /sys/fs/bpf/token2
	allowed_cmds:
	  map_create          prog_load
	allowed_maps:
	allowed_progs:
	  kprobe
	allowed_attachs:
	  xdp

Example json output for `token show`:
[{
	"token_info": "/sys/fs/bpf/token",
	"allowed_cmds": ["map_create", "prog_load"],
	"allowed_maps": [],
	"allowed_progs": ["kprobe"],
	"allowed_attachs": ["xdp"]
}, {
	"token_info": "/sys/fs/bpf/token2",
	"allowed_cmds": ["map_create", "prog_load"],
	"allowed_maps": [],
	"allowed_progs": ["kprobe"],
	"allowed_attachs": ["xdp"]
}]

Reviewed-by: Quentin Monnet <qmo@kernel.org>
Signed-off-by: Tao Chen <chen.dylane@linux.dev>
Link: https://lore.kernel.org/r/20250723144442.1427943-1-chen.dylane@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

tools/bpf/bpftool/main.c

@@ -61,7 +61,7 @@ static int do_help(int argc, char **argv)
 		"       %s batch file FILE\n"
 		"       %s version\n"
 		"\n"
-		"       OBJECT := { prog | map | link | cgroup | perf | net | feature | btf | gen | struct_ops | iter }\n"
+		"       OBJECT := { prog | map | link | cgroup | perf | net | feature | btf | gen | struct_ops | iter | token }\n"
 		"       " HELP_SPEC_OPTIONS " |\n"
 		"                    {-V|--version} }\n"
 		"",
@@ -87,6 +87,7 @@ static const struct cmd commands[] = {
 	{ "gen",	do_gen },
 	{ "struct_ops",	do_struct_ops },
 	{ "iter",	do_iter },
+	{ "token",	do_token },
 	{ "version",	do_version },
 	{ 0 }
 };

tools/bpf/bpftool/main.h

@@ -166,6 +166,7 @@ int do_tracelog(int argc, char **arg) __weak;
 int do_feature(int argc, char **argv) __weak;
 int do_struct_ops(int argc, char **argv) __weak;
 int do_iter(int argc, char **argv) __weak;
+int do_token(int argc, char **argv) __weak;
 
 int parse_u32_arg(int *argc, char ***argv, __u32 *val, const char *what);
 int prog_parse_fd(int *argc, char ***argv);

tools/bpf/bpftool/token.c

@@ -0,0 +1,225 @@
+// SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+/* Copyright (C) 2025 Didi Technology Co., Tao Chen */
+
+#ifndef _GNU_SOURCE
+#define _GNU_SOURCE
+#endif
+#include <errno.h>
+#include <fcntl.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <mntent.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+
+#include "json_writer.h"
+#include "main.h"
+
+#define MOUNTS_FILE "/proc/mounts"
+
+static bool has_delegate_options(const char *mnt_ops)
+{
+	return strstr(mnt_ops, "delegate_cmds") ||
+	       strstr(mnt_ops, "delegate_maps") ||
+	       strstr(mnt_ops, "delegate_progs") ||
+	       strstr(mnt_ops, "delegate_attachs");
+}
+
+static char *get_delegate_value(const char *opts, const char *key)
+{
+	char *token, *rest, *ret = NULL;
+	char *opts_copy = strdup(opts);
+
+	if (!opts_copy)
+		return NULL;
+
+	for (token = strtok_r(opts_copy, ",", &rest); token;
+			token = strtok_r(NULL, ",", &rest)) {
+		if (strncmp(token, key, strlen(key)) == 0 &&
+		    token[strlen(key)] == '=') {
+			ret = token + strlen(key) + 1;
+			break;
+		}
+	}
+	free(opts_copy);
+
+	return ret;
+}
+
+static void print_items_per_line(const char *input, int items_per_line)
+{
+	char *str, *rest, *strs;
+	int cnt = 0;
+
+	if (!input)
+		return;
+
+	strs = strdup(input);
+	if (!strs)
+		return;
+
+	for (str = strtok_r(strs, ":", &rest); str;
+			str = strtok_r(NULL, ":", &rest)) {
+		if (cnt % items_per_line == 0)
+			printf("\n\t  ");
+
+		printf("%-20s", str);
+		cnt++;
+	}
+
+	free(strs);
+}
+
+#define ITEMS_PER_LINE 4
+static void show_token_info_plain(struct mntent *mntent)
+{
+	char *value;
+
+	printf("token_info  %s", mntent->mnt_dir);
+
+	printf("\n\tallowed_cmds:");
+	value = get_delegate_value(mntent->mnt_opts, "delegate_cmds");
+	print_items_per_line(value, ITEMS_PER_LINE);
+
+	printf("\n\tallowed_maps:");
+	value = get_delegate_value(mntent->mnt_opts, "delegate_maps");
+	print_items_per_line(value, ITEMS_PER_LINE);
+
+	printf("\n\tallowed_progs:");
+	value = get_delegate_value(mntent->mnt_opts, "delegate_progs");
+	print_items_per_line(value, ITEMS_PER_LINE);
+
+	printf("\n\tallowed_attachs:");
+	value = get_delegate_value(mntent->mnt_opts, "delegate_attachs");
+	print_items_per_line(value, ITEMS_PER_LINE);
+	printf("\n");
+}
+
+static void split_json_array_str(const char *input)
+{
+	char *str, *rest, *strs;
+
+	if (!input) {
+		jsonw_start_array(json_wtr);
+		jsonw_end_array(json_wtr);
+		return;
+	}
+
+	strs = strdup(input);
+	if (!strs)
+		return;
+
+	jsonw_start_array(json_wtr);
+	for (str = strtok_r(strs, ":", &rest); str;
+			str = strtok_r(NULL, ":", &rest)) {
+		jsonw_string(json_wtr, str);
+	}
+	jsonw_end_array(json_wtr);
+
+	free(strs);
+}
+
+static void show_token_info_json(struct mntent *mntent)
+{
+	char *value;
+
+	jsonw_start_object(json_wtr);
+
+	jsonw_string_field(json_wtr, "token_info", mntent->mnt_dir);
+
+	jsonw_name(json_wtr, "allowed_cmds");
+	value = get_delegate_value(mntent->mnt_opts, "delegate_cmds");
+	split_json_array_str(value);
+
+	jsonw_name(json_wtr, "allowed_maps");
+	value = get_delegate_value(mntent->mnt_opts, "delegate_maps");
+	split_json_array_str(value);
+
+	jsonw_name(json_wtr, "allowed_progs");
+	value = get_delegate_value(mntent->mnt_opts, "delegate_progs");
+	split_json_array_str(value);
+
+	jsonw_name(json_wtr, "allowed_attachs");
+	value = get_delegate_value(mntent->mnt_opts, "delegate_attachs");
+	split_json_array_str(value);
+
+	jsonw_end_object(json_wtr);
+}
+
+static int __show_token_info(struct mntent *mntent)
+{
+	if (json_output)
+		show_token_info_json(mntent);
+	else
+		show_token_info_plain(mntent);
+
+	return 0;
+}
+
+static int show_token_info(void)
+{
+	FILE *fp;
+	struct mntent *ent;
+
+	fp = setmntent(MOUNTS_FILE, "r");
+	if (!fp) {
+		p_err("Failed to open: %s", MOUNTS_FILE);
+		return -1;
+	}
+
+	if (json_output)
+		jsonw_start_array(json_wtr);
+
+	while ((ent = getmntent(fp)) != NULL) {
+		if (strncmp(ent->mnt_type, "bpf", 3) == 0) {
+			if (has_delegate_options(ent->mnt_opts))
+				__show_token_info(ent);
+		}
+	}
+
+	if (json_output)
+		jsonw_end_array(json_wtr);
+
+	endmntent(fp);
+
+	return 0;
+}
+
+static int do_show(int argc, char **argv)
+{
+	if (argc)
+		return BAD_ARG();
+
+	return show_token_info();
+}
+
+static int do_help(int argc, char **argv)
+{
+	if (json_output) {
+		jsonw_null(json_wtr);
+		return 0;
+	}
+
+	fprintf(stderr,
+		"Usage: %1$s %2$s { show | list }\n"
+		"       %1$s %2$s help\n"
+		"\n"
+		"",
+		bin_name, argv[-2]);
+	return 0;
+}
+
+static const struct cmd cmds[] = {
+	{ "show",	do_show },
+	{ "list",	do_show },
+	{ "help",	do_help },
+	{ 0 }
+};
+
+int do_token(int argc, char **argv)
+{
+	return cmd_select(cmds, argc, argv, do_help);
+}